When it comes to memory, many people share similar feelings:

My memory has really been getting worse over the past few years.

I unlock my phone one second, and the next I have no idea what I was about to do.

Wait—when did I order this package? I have absolutely no memory of it…

What did I eat last night? What did I do? Total blank.

…

Same here. Just now, I noticed an opened can of soda sitting on my desk, yet I have zero recollection of when I took it out of the fridge. Could it be the legendary “snail girl” secretly helping me out? Impossible! Don’t tell me I’m getting Alzheimer’s?!

Hold on—no need to panic just yet. This doesn’t mean your brain is sick, nor is it necessarily a sign of aging. What we often call “poor memory” or “being forgetful” is usually the result of misunderstanding how the brain actually works, mistaking its normal functions for bugs. Trying to fix everyday forgetfulness by practicing complex mnemonic techniques like the “memory palace” is often overkill—hard to stick with and largely unnecessary.¹

In contrast, understanding how your brain operates and adjusting your thinking patterns and daily habits is a much easier and more effective solution.

Phenomenon 1: Forgetting as Soon as You Turn Around — What Was I About to Do Again?

Many people have experienced this “forget-as-soon-as-you-turn-around” moment: you unlock your phone intending to quickly check the weather or track a delivery. Then you see a WeChat notification and tap into it. Just a few seconds later, when you return to the home screen, you freeze—why did I unlock my phone in the first place?

This isn’t a problem that only appeared after smartphones became widespread. Similar phenomena have existed for a long time. In psychology, there’s a specific term for it: the “doorway effect.” You think of something you need to do—say, grabbing a pair of socks from the bedroom—but once you step through the doorway into the bedroom, you may forget why you went there.

Psychological experiments have further confirmed this effect. Researchers randomly picked up objects from a table and placed them into a box, then later asked participants to recall what was in the box. In one group, participants stayed in the same room. In the second group, they moved to another room to recall. In the third group, they stepped out briefly and then returned to the original room.

Even though the recall intervals were the same for all three groups, the latter two showed significantly more forgetting. The root of this phenomenon isn’t “memory capacity,” but rather “attention.”

Working Memory vs. Long-Term Memory

First, a brief introduction. Many people are familiar with the distinction between working memory (short-term memory) and long-term memory.²

Working memory is the system the brain uses to temporarily store and process information. You can think of it as a type of short-term memory. Its characteristics are a very short retention time and a limited capacity³—if information isn’t deeply processed, it can disappear within seconds or tens of seconds.

Corresponding to it is long-term memory. Long-term memory is like a vast warehouse, capable of storing memories in large quantities over long periods of time. The knowledge we’ve learned, our life experiences, and skills like riding a bike, swimming, or writing are all stored there.

You can imagine working memory as a temporary workbench with a conveyor belt. Packages on this bench come from two main sources: one is external sensory information, such as what you see or hear; the other is internally generated thoughts or memories retrieved from long-term memory, such as “go get socks” or “check the delivery status.”

There’s one crucial role here: the sorter at the temporary workbench—attention.

Because working memory has limited capacity, only the packages that attention keeps a close eye on can stay on the workbench long enough to be further processed and stored in long-term memory. The moment attention slips, those packages slide off the bench and are gone for good.

Back to the doorway effect. Whether it’s entering a new room or opening a new app, both are essentially scene switches. During such transitions, a flood of new sensory information rushes in—lighting, layout, colors, sounds, and more. Even if you’re not consciously aware of it, these external stimuli objectively hijack your attention, causing the original thought in your mind, or the sensory information you just captured, to be cleared from the limited workbench of working memory. When you snap back, the workbench is empty, and the original package is nowhere to be found.

That’s why you end up standing there, spaced out, unable to remember what you were just about to do.

How to Deal With the Doorway Effect

The doorway effect is an instinct the brain evolved to adapt to new environments. It’s very similar to a computer clearing cache and freeing up memory so it can better load new programs and handle uncertainties in a new context. This is actually a sign of efficient brain operation. There’s no need to fight against this biological mechanism, let alone blame it on having a “bad memory.”

Since the core issue is that scene changes shift attention, the countermeasures are straightforward: either protect your attention from being hijacked, or reduce the load on working memory in advance.

1. Reduce distractions. The most direct way to deal with the doorway effect is to avoid attention shifts. Put frequently used items (such as scissors, keys, or your phone) in fixed, visible locations. Place high-frequency apps (like weather or payments) on your phone’s home screen or use widgets. By shortening the time and steps needed to find your target, you reduce the risk of being distracted by irrelevant information, allowing attention to go straight to the task.
2. Repeat it out loud. When memorizing a phone number or license plate, we often repeat the digits to reinforce memory. The same applies here. When you’re about to go from the living room to the bedroom to get socks, or unlock your phone to check a delivery in a shopping app, quietly say it out loud: “get socks, get socks,” or “check delivery, check delivery.” Repetition forcefully locks attention onto the working memory task, preventing it from being replaced by new environmental information.
3. Write it down. If you’re going into a room to get more than three items, or opening your phone to handle several tasks, the best approach isn’t relying on your brain but writing things down. To avoid the act of finding pen and paper becoming a new distraction, it’s a good idea to keep them within easy reach at home. Many people also pin notes or to-do list widgets to their phone’s home screen or set up shortcuts—these are effective strategies as well.
4. Recreate the context. If you’ve already fallen victim and simply can’t remember what you were about to do, the best move is to go back to where the thought originated. If it came to you in the living room, go back to the living room. If it occurred while browsing a specific webpage, return to that page. Our memories are often bound to their environments, and the visual or auditory cues from that moment can reactivate the brain, helping you recover the lost memory trail.

Phenomenon 2: Everyday Blackouts — What Did I Have for Breakfast Again?

Besides forgetting things the moment you turn around, another everyday phenomenon that often makes people question their memory is these “blackouts” around mundane details. Most of us are probably familiar with situations like these:

• You’ve just walked downstairs a few steps when a sudden wave of anxiety hits: Did I lock the door? Did I turn off the lights? Sometimes you even run back to check before you can relax.
• Halfway through a shower, shampoo bottle in hand, you pause: Wait—did I already wash my hair, or was I just about to?
• You take public transport or drive home after work and realize you can’t recall any details of the commute, as if you’d teleported. This becomes even more obvious when you’re tired, sleepy, or lost in thought.
• Where did you eat lunch today, yesterday, or the day before? What did you eat? Chances are, unless you check your food delivery history, you won’t remember much at all.

Everyone carries memories of their own life. This type of memory belongs to long-term memory and is called “episodic memory.” Some memories are so vivid that they remain crystal clear years later. Others, though they happened not long ago, leave only the faintest trace.

Episodic memory has a unique feature: you don’t just remember what happened, but also when and where it happened. In other words, these memories come with “time stamps” and “location tags.”

However, when it comes to highly repetitive and trivial daily episodes, the brain becomes surprisingly clever—or, from another perspective, surprisingly stingy. That’s when blackouts and forgetfulness start to appear.

Everyday Memories: Merged and Compressed

For daily routines like commuting, eating three meals a day, or washing your face and brushing your teeth—activities that are highly repetitive and emotionally flat—the brain usually performs an automatic “merge similar items” operation to save cognitive resources.

Take breakfast as an example. Every morning, around 8 a.m., you take a bottle of milk and a ready-to-eat soft-boiled egg from the fridge, grab a slice of bread from the table, and spend five minutes eating at your dining table. Because the scene and content of breakfast barely change from day to day, the brain doesn’t store each breakfast as a separate memory file. Instead, it compresses thousands of past breakfasts into a single, generic, fuzzy “template file.”

So when you try to recall what you had for breakfast yesterday, the brain first retrieves this generic template: the dining table at home, plus the usual trio of milk, eggs, and toast—rather than a specific snapshot of yesterday morning. And since yesterday’s breakfast had nothing particularly distinctive about it, lacking any standout features, that memory gets submerged into the routine, creating the illusion that you’ve forgotten it.

Abnormal Memories: Individually Tagged and Stored

So when do we clearly remember an episode? The answer is: when routine is broken.

Anyone who has used smart security cameras will know about a standard feature called “motion detection.” When the scene is static and nothing changes—say, an empty hallway—the footage is overwritten in a loop, taking up minimal storage. Only when movement is detected, such as a delivery person passing by, do additional functions kick in and the footage gets saved long-term.

Our brains use a similar mechanism when recording daily events. Back to breakfast: imagine that one morning, instead of milk and toast, you decide to cook a bowl of luosifen, filling the house—and yourself—with its unmistakable smell. This highly distinctive breakfast would trigger the brain’s recording mode. The brain detects the anomaly, slaps on a bright label, and archives it separately. Even years later, you’d still remember the embarrassment of eating luosifen for breakfast and getting side-eyed by fellow commuters on the subway.

So if you can’t remember what you had for lunch last Wednesday, or what happened on yesterday’s subway ride, there’s no need to blame your memory. Everyday blackouts are a sign that your life is regular and stable, and that your brain is running smoothly, compressing those unremarkable daily memories to free up precious space for truly unique and important life events.

How to Deepen Episodic Memory

Once you understand how episodic memory works, the reverse is also true: if you want to remember something in daily life, or make a memory more vivid, you need to intervene actively and give it more distinctive features.

Here are a few effective methods:

• Engage multiple senses. If you’re experiencing a special moment—say, an anniversary dinner with your partner—and want to imprint it deeply in your mind, actively engage multiple senses. Smell the aroma of the food, notice the unique patterns on the tableware, listen to the background music, feel the texture of the chair. The more sensory details you collect, the richer the memory becomes, and the less likely the brain is to treat it as just another ordinary event and merge it into a generic template.
• Leave traces. Many people struggle with forgetting whether they’ve taken their medication, especially when it needs to be taken regularly over long periods. At that point, taking medicine has become an automated action, leaving little impression in memory. “Leaving traces” is an effective way to remember such repetitive events. For example, place a calendar or sticky note next to the medicine bottle and check it off each time. Or follow medical advice and bind taking medication to another routine with the same cycle—put morning and evening meds next to your toothbrush and make a rule that you can only brush your teeth after taking them. This way, brushing your teeth reinforces taking medicine, and whether you’ve brushed your teeth also tells you if you’ve taken your meds.
• Ritualized actions. For everyday compulsive behaviors, adding a fixed ritual can be very effective. When locking the door or turning off the gas, for instance, introduce a ritual check, such as the “point-and-call” method commonly used in industrial settings: point at the gas valve or lock, look at it, and say out loud, “Gas off,” “Door locked,” before leaving. This ritual labels the otherwise subconscious action, making it easier to retrieve later. If compulsive behaviors are severe, they may stem from physiological, psychological, or environmental factors and require professional medical treatment.
• Write it down. It must be admitted that even with rich sensory input, special cues, and ritualized actions, the brain is still not good at remembering repetitive life details. The most reliable approach is to lighten the brain’s load by using a “second brain”—external tools. For example, every time I park in a mall now, the first thing I do is take a photo of the floor number and parking spot. Precious memories with friends and family are stored in photo albums, and I’ve developed the habit of journaling, supplemented by chat histories, browser history, and emails to aid recall and retrieval.

Common methods for strengthening episodic memory (AI-generated image)

Of course, as we age, the hippocampus—the brain region responsible for episodic memory—does gradually decline in function. This is a natural physiological process. So if you find your episodic memory isn’t as sharp as it used to be, don’t be overly anxious or self-critical. Accept a certain degree of forgetting in daily life, and save your limited energy for the people and moments truly worth remembering—that’s the best way to face time and aging.

Phenomenon 3: Read It, Forgot It — What Was That Article About Again?

Today’s learning tools and productivity apps are more convenient than ever. Notes used to be handwritten; now OCR lets you copy text with a tap. Research used to mean clipping and filing; now browser extensions save everything instantly. Long articles once required careful reading, books page by page; now AI can summarize everything in a minute.

Behind this smooth flow of collecting, hoarding, and speed-reading, however, lies an easy-to-fall-into illusion of understanding. Many people notice that articles they’ve read and knowledge they’ve learned seem easier to forget than before. It can feel like learning ability has declined or memory has worsened. In reality, this is often the result of inappropriate learning methods.

Many members of the community have written about this before. In earlier articles discussing learning principles and core elements, I also went into detail about how to address this issue (see the third section). If you’re interested, you can check those out. Here, I’ll explain from the perspective of memory mechanisms why this “learn fast, forget fast” phenomenon happens.

Storage Strength vs. Retrieval Strength

Earlier, we talked about episodic memory, which is a type of long-term memory.

Long-term memory has many forms. The one most closely related to learning is called semantic memory. You can think of it as the brain’s database or library: all the knowledge points, facts, concepts, vocabulary, and formulas you learn are stored there.

When learning, many people—including myself—often feel that they have a bad memory and forget things right after learning them. Strictly speaking, though, “forgetting” isn’t an accurate description. From a cognitive psychology perspective, information that has truly been stored in long-term memory is extremely difficult to erase completely. As mentioned earlier, long-term memory is like a vast warehouse: once something is learned, it’s placed inside. The real problem is usually not that the memory is gone, but that the index is lost—the cue pointing to that memory can’t be found.

Psychologists Robert and Elizabeth Bjork proposed that memory has two independent measures: storage strength and retrieval strength (Bjork, 1992).

Storage strength refers to how firmly something is retained once it has been learned. This view challenges the traditional idea that “memories fade,” arguing instead that once long-term memory is formed, it is stored in the brain almost permanently. Retrieval strength, on the other hand, refers to whether you can access that memory at a given moment—how easily it comes to mind. What we usually call “forgetting after remembering” is actually a weakening of retrieval strength: the memory is there, but hard to retrieve.

Combining these two dimensions gives us four types of memory states:

• Low storage strength + low retrieval strength: shallow memories that are easy to forget.

For example, an article skimmed casually, or a piece of trivia glanced at in a short video. We’ve all had this experience: you’re almost done with a book, movie, or post, and suddenly realize—wait, I’ve seen this before? Because it was never deeply processed, it left only the faintest trace in the brain. Without rereading or rewatching, you’d never be able to retrieve it. This is the worst-hit area for “knowledge hoarding.”

• Low storage strength + high retrieval strength: shallow memories that haven’t faded yet.

Crammed exam material, a restaurant queue number, a hotel room number on a business trip, or the plot of a mystery series binged overnight all fall into this category. Right now, the content feels clear, giving you the illusion that you’ve “remembered” it. In reality, storage strength is low, and once the task ends—after the exam, checkout, or finishing the meal—it quickly disappears. These memories are often tied to cramming and massed practice, and are best reinforced with spaced repetition.

• High storage strength + low retrieval strength: firmly stored memories you can’t recall at the moment.

Think of an old QQ number you used for years, familiar English words you haven’t used in ages, or a song you haven’t sung for decades. These memories aren’t gone; they still exist deep in your brain. But because they haven’t been used in a long time, they don’t come to mind immediately. For this type of knowledge, you usually don’t need to relearn it from scratch. A small cue—like being told the first two digits of the QQ number—can reactivate the memory. Regular maintenance and occasional review are enough.

• High storage strength + high retrieval strength: memories that are solid and instantly accessible.

Basic facts (China’s capital, the multiplication table), your own birthday, a phone password you’ve never changed, or gossip about an idol you’ve followed for years all fit here. No matter your state, you can recall these without effort. This knowledge has been fully internalized and become part of you. This is what it truly means to have “learned” something. The ultimate goal of learning is to move knowledge from the earlier categories into this automated state.

The “Desirable Difficulty” of Better Memory

Looking across these four categories, a pattern emerges. Learning methods that feel comfortable and frictionless tend to fall into either ineffective hoarding (“low storage + low retrieval”), such as one-click saving, photographing lecture slides, or endlessly downloading resources; or cramming modes (“low storage + high retrieval”), such as rereading, highlighting, immediately checking answers, or following tutorials step by step. These approaches don’t build durable memory—and the issue isn’t memory ability itself.

So what’s the right approach? The Bjorks proposed a counterintuitive theory called “desirable difficulties” (Bjork, 1994). It explains a core mechanism of memory: increases in storage strength are inversely related to current retrieval strength. In simple terms, the harder it feels to retrieve information now, the deeper it will take root in your brain later.

This may sound abstract, but anyone with fitness experience will recognize it. Easy learning is like lifting an empty barbell: you can do it effortlessly, but without tearing muscle fibers, there’s no growth. In contrast, lifting with proper form to the point of fatigue causes muscle fibers to tear, followed by rebuilding and strengthening.

The same applies to learning. Reviewing new knowledge immediately often yields mediocre results. The most effective approach is to allow some forgetting, then close the book and actively recall what you learned. This process may make you frown, scratch your head, and feel mentally stuck—but that discomfort is precisely what most effectively strengthens storage.

What Is Forgetting Actually Good For?

Once we understand different memory mechanisms, we can take a fresh look at the meaning of “forgetting.” In the learning process, forgetting is far from useless—in fact, you could even say that without forgetting, there would be no learning at all. It plays three crucial roles:

First, at the working memory stage, it acts as a filter for attention.

As mentioned in the first section, an overload of information from the environment can overwhelm the brain. Forgetting helps filter out irrelevant interference, allowing the brain to focus on what matters most. It functions as a selection mechanism: only information that is truly valuable has a chance to be further processed and stored in long-term memory.

Second, at the long-term memory stage, it is a necessary condition for strengthening storage and forming cognitive abstraction.

According to the theory of “desirable difficulties,” forgetting actually creates the necessary difficulty. Precisely because forgetting lowers retrieval strength, you have to exert effort to recall; and precisely because that effort is required, the brain judges the information to be important, significantly increasing its storage strength.

In addition, forgetting helps us discard trivial details and extract the essence, enabling better abstraction and generalization. It’s like recognizing a face: when you first meet someone, you may remember many detailed features—skin condition, hairstyle, makeup. But later, when you see them again, their hairstyle or makeup may have changed, yet you still recognize them. That’s because the brain has helped you forget certain details, allowing you to better generalize their facial characteristics and form a stable, lasting memory model.

Third, at the level of everyday life, it is an essential means for maintaining inner order and adapting to the present environment.

Imagine if every heartbreak or every awkward moment remained as vivid and intense as when it first happened—our minds would be overwhelmed long ago. Through forgetting, the brain strips away the emotional overload from memories, leaving us with lessons learned while gradually fading the sharp pain, allowing us to recover from trauma. Forgetting also clears out outdated knowledge. For example, when you move to a new home, you must let go of the old address and routes so the new ones can be stored smoothly. If old memories never faded, they would linger like ghosts, constantly interfering with present life and causing far more trouble than we might expect.

If a person were unable to forget anything, their brain would instead descend into chaos due to information overload, resulting in impaired cognitive function.

There was a memory prodigy in the Soviet Union named Shereshevsky, who possessed an almost limitless memory. Yet because he could not forget, his brain was flooded with massive amounts of sensory detail. This left him severely lacking in abstraction: he couldn’t grasp poetic metaphors or perform complex logical reasoning.

A similar phenomenon can be observed in some individuals with high-functioning autism. They can record scenes like a camera, but precisely because the details are too numerous and too vivid, this abundance hinders their ability to understand the social context and core meaning behind a scene. Even minor environmental changes can make them feel uneasy and anxious. This again shows that without pruning details, the brain cannot build meaningful models. In this sense, everyday forgetfulness is often the brain performing routine “garbage collection” and information filtering to maintain efficient operation—it is not the functional decline we so often fear.

With these principles in mind, if we revisit the memory-strengthening methods discussed in the previous article—such as active engagement, writing, spaced repetition, and sleep—their logic becomes much clearer. There’s no need to repeat them here.

Summary

Although we talk about memory and forgetting every day, memory is not a single, unified ability, and forgetting is not an entirely bad thing.

In this article, we discussed working memory and long-term memory, and within long-term memory, the declarative (explicit) forms of episodic memory and semantic memory. Due to space limitations, another important member of the long-term memory family—procedural memory, which belongs to non-declarative memory and includes skills like tying shoelaces, riding a bike, or reading in one’s native language—was not covered here. If there’s an opportunity in the future, I’ll dedicate a separate piece to it under the theme of “practice.”

If there’s interest, I’d also like to write another article exploring common memory disorders and classic cases—such as age-related memory decline, the tip-of-the-tongue phenomenon, or even severe amnesia caused by illness—to further deepen our understanding of how memory works.

Further reading: Incomplete Reports on the Use of Attention

1. This isn’t to say the Memory Palace method is useless. It’s more suited for situations where you need to cram large amounts of illogical information into your memory in a short time—like memorizing the order of playing cards, pi, or lists of obscure vocabulary—rather than for tackling everyday forgetfulness issues like those mentioned above.
   
   
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2. Strictly speaking, the field of psychology features numerous schools of thought regarding memory models (such as the Baddeley model, which incorporates complex structures like the central executive system and phonological loop), and definitions of working memory and short-term memory also vary. For the sake of clarity, this paper employs a simplified, universal model and does not make a strict distinction between the two at this stage.
   
   
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3. Earlier research suggested that working memory could hold at most 7±2 items (Miller, 1956); current studies generally agree that its actual capacity is around 4 “chunks.” For instance, we struggle to memorize 10 random digits, but grouping them into sets of three—such as years or phone numbers—makes recall effortless. Each set of digits here constitutes a chunk. ↩︎